Recently, two-dimensional array transducers are beginning to be used in ultrasonic probes, so the number of transducers has increased to several thousands, and the size of each individual transducer has extremely decreased. Connecting an ultrasonic probe directly to an ultrasonic diagnostic apparatus of this type requires a large-diameter cable in which very many electronic lines can be inserted. The use of this large-diameter cable interferes with operations, and makes it difficult to efficiently transmit a driving waveform to a microtransducer, and transmit a high-quality ultrasonic echo received by a microtransducer. For an ultrasonic probe using two-dimensional array transducers, therefore, the efficiency of the driving of microtransducers and the efficiency of the amplification of an ultrasonic echo are increased by incorporating electronic circuits such as a transmitting circuit and receiving circuit in a probe handle. In addition, the number of signal lines input to an ultrasonic diagnostic apparatus is often reduced by performing partial receiving beam forming for every several transducers and adding the results.
FIG. 1 shows the arrangement of an ultrasonic diagnostic apparatus of this type. This ultrasonic diagnostic apparatus includes an ultrasonic probe 100 including a probe handle 110 and a probe connector 130 connected to the handle 110 via a probe cable 120, and an ultrasonic diagnostic apparatus main body 150 connected to the probe connector 130 via a main body probe connector 140.
The probe handle 110 includes transducers 111 arranged in the form of an array, pulsers 112 for generating an ultrasonic beam having a predetermined directionality by driving the transducers 111, preamplifiers 113 for performing processing such as low-noise amplification or buffering for satisfactorily transmitting very small ultrasonic echo signals received by the transducers 111, a sub-array beam former 114 for adding output signals from the preamplifiers 113 by giving a delay time to each group of a few channels, thereby reducing the number of output signal lines from the probe handle 110, and a control circuit 115 for controlling the individual components in the probe handle 110.
The probe connector 130 includes electronic circuits 131 for performing additional processing such as amplification, buffering, or band adjustment on ultrasonic echo signals as needed, and a probe connector control circuit 132 for generating a control signal to be transmitted to the control circuit 115 of the probe handle 110, based on a control signal transmitted from the ultrasonic diagnostic apparatus main body 150.
The ultrasonic diagnostic apparatus main body 150 includes main body preamplifiers 151 for amplifying the ultrasonic echo signals to which the delay is added for each group of a few channels in the probe handle 110, a reception delay addition circuit 152 for matching the timings of the amplified signals, a signal processing unit 153 for detecting the signals and extracting the envelope, an image processing unit 154 for transforming coordinates in accordance with the section of the object, a display unit 155 for displaying image data having the transformed coordinates, a main body control circuit 156 for controlling each unit, an operation panel 157 for accepting user's operations, a main body transmission delay circuit 158, and main body pulsers 159. The main body transmission delay circuit 158 and main body pulsers 159 operate a probe incorporating no electronic circuits when the probe is connected instead of the ultrasonic probe 100. This ultrasonic diagnostic apparatus can also detect and process the Doppler shift frequency of an ultrasonic beam resulting from the movement of blood cells generated when ultrasonic waves are exchanged with a blood flow in an object to be examined, and display blood flow velocity information as a Doppler image.
Since the ultrasonic wave transmitting and receiving processes are performed in the probe handle 110 as described above, electric power must be supplied to the built-in electronic circuits of the probe handle 110. However, to obtain, from an object to be examined, high-quality ultrasonic signals that can contribute to diagnosis, it is necessary to maintain a high transmitting/receiving performance by supplying considerable electric power. Consequently, the built-in electronic circuits generate heat and raise the temperature. This state interferes with operations, and may damage the object because the heat is conducted to the surface in contact with the object. Furthermore, the built-in electronic circuits themselves may break.
If the amount of power supplied to the probe handle 110 is reduced, however, the performance degrades to make it impossible to obtain necessary information, thereby interfering with diagnosis. Recently, therefore, a two-dimensional (2D) array probe including a cooling unit for cooing a probe handle by circulating a coolant is particularly beginning to be used.
FIG. 2 shows an example of the cooling unit using a coolant. This cooling unit includes a heat absorbing unit 160 in which a coolant channel is formed, a cooling device 162 connected to the channel of the heat absorbing unit 160 by cooling tubes 161a and 161b, and a cooling control circuit 163 for controlling the cooling device 162.
The cooling device 162 includes a pump for circulating the coolant, a radiator having a large number of radiation fins, and a cooling fan for supplying cooling air to the radiator. Under the control of the cooling control circuit 163, the cooling device 162 circulates the coolant by driving the built-in pump, and cools the coolant by rotating the cooling fan. The cooled coolant is supplied to the heat absorbing unit 160, and takes heat from circuits of a probe handle 110. This prevents the temperature rise of the circuits.
When attaching the cooling unit as described above, however, a very small forced cooling system is necessary because the volume of the probe handle is only about 100 cc. This complicates the structure of the ultrasonic probe, and probably makes it impossible to secure a sufficient durability. Also, it is difficult to obtain a sufficient cooling performance because the installation space of the cooling unit is limited. Furthermore, if the cooling unit fails, it is difficult to repair the fault cooling unit, so an expensive ultrasonic probe must be discarded.
Under the circumstances, demands have arisen for an ultrasonic probe in which the structure of a probe handle is a simple structure similar to a natural air cooling structure, and a forced cooling unit can easily be replaced even if it fails.